00001 /*This file has been prepared for Doxygen automatic documentation generation.*/ 00015 /* Copyright (c) 2009 Atmel Corporation. All rights reserved. 00016 * 00017 * Redistribution and use in source and binary forms, with or without 00018 * modification, are permitted provided that the following conditions are met: 00019 * 00020 * 1. Redistributions of source code must retain the above copyright notice, this 00021 * list of conditions and the following disclaimer. 00022 * 00023 * 2. Redistributions in binary form must reproduce the above copyright notice, 00024 * this list of conditions and the following disclaimer in the documentation 00025 * and/or other materials provided with the distribution. 00026 * 00027 * 3. The name of Atmel may not be used to endorse or promote products derived 00028 * from this software without specific prior written permission. 00029 * 00030 * 4. This software may only be redistributed and used in connection with an Atmel 00031 * AVR product. 00032 * 00033 * THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED 00034 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 00035 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE 00036 * EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR 00037 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 00038 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 00039 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 00040 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 00041 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 00042 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE 00043 * 00044 */ 00045 #include "dsp.h" 00046 #include "preprocessor.h" 00047 00048 #if defined(FORCE_ALL_GENERICS) || \ 00049 defined(FORCE_GENERIC_OP16_LN) || \ 00050 !defined(TARGET_SPECIFIC_OP16_LN) 00051 00052 S32 dsp16_op_ln_raw(dsp16_t num) 00053 { 00054 dsp16_t num_temp; 00055 S32 a, a_sqr, res; 00056 int under_bit_val; 00057 00058 // Limit 00059 if (num <= DSP16_Q(0.)) 00060 return DSP_Q_MIN(DSP16_QA, DSP16_QB); 00061 00062 // get ~ int(log2(num)) 00063 // num is in the range [1; 0.5] 00064 if (num > DSP16_Q(1.)) 00065 { 00066 under_bit_val = 0; 00067 num_temp = num; 00068 while (num_temp > DSP16_Q(1.)) 00069 { 00070 num_temp >>= 1; 00071 under_bit_val++; 00072 } 00073 num_temp = (num >> under_bit_val); 00074 } 00075 else 00076 { 00077 under_bit_val = 0; 00078 num_temp = num; 00079 while (num_temp < DSP16_Q(0.5)) 00080 { 00081 num_temp <<= 1; 00082 under_bit_val++; 00083 } 00084 num_temp = (num << under_bit_val); 00085 } 00086 00087 // << (DSP16_QB - 1) to avoid overflows 00088 a = (((S32) num_temp) - DSP16_Q(1.)) << DSP16_QB; 00089 a = a/(((S32) num_temp) + DSP16_Q(1.)); 00090 // calculate a^2 00091 a_sqr = (a*a) >> DSP16_QB; 00092 00093 res = (a_sqr*DSP16_Q(1./9.)) >> DSP16_QB; 00094 res = (a_sqr*(res + DSP16_Q(1./7.))) >> DSP16_QB; 00095 res = (a_sqr*(res + DSP16_Q(1./5.))) >> DSP16_QB; 00096 res = (a_sqr*(res + DSP16_Q(1./3.))) >> DSP16_QB; 00097 res = (a*(res + DSP16_Q(1.))) >> (DSP16_QB - 1); 00098 00099 if (num > DSP16_Q(1.)) 00100 res += ((S32) under_bit_val)*((S32) DSP16_Q(CST_LN_2)); 00101 else 00102 res -= ((S32) under_bit_val)*((S32) DSP16_Q(CST_LN_2)); 00103 00104 return res; 00105 } 00106 00107 #endif